1. Field of the Invention
The present invention relates to information acquiring apparatuses and methods for obtaining information, such as characteristics, of an object by using electromagnetic radiation. More particularly, the present invention relates to information acquiring apparatuses and methods for obtaining information of an object by using terahertz (THz) radiation.
2. Description of the Related Background Art
In this specification, the terminology “terahertz (THz) radiation”, or the like is used for electromagnetic radiation containing a radiation component in a frequency range between about 30 GHz and about 30 THz. In recent years, non-destructive sensing technology using terahertz radiation has been developed and searched. Technical fields using such terahertz radiation include imaging fields using safe see-through examining apparatuses in place of X-ray apparatuses.
Further, development has also been made with respect to spectroscopic technology for acquiring absorption spectra and complex dielectric constants to examine characteristics, such as bonding condition, of substances, analytic technology for analyzing bio-molecules, estimating technology for estimating carrier concentration and mobility, and the like. An example of application of the above technology includes an apparatus of examining a component or particle size of medicine in a medicine producing process. It is desired to develop an examining apparatus utilizing features of terahertz radiation and capable of non-destructive in-process measurement.
A typical spectroscopic analyzing method using terahertz radiation includes the terahertz time domain spectroscopy (THz-TDS). The THz-TDS is capable of measuring the time domain waveform of electric field intensity of a terahertz pulse. JP 2006-526774 A (corresponding to US2006237650) discloses technology of Fourier-transforming the time domain waveform to acquire its spectrum, and identifying component of an object by an analyzing method using calibration curves or the like.
When a component or particle size of an object is measured in an in-process manner during a step of transporting, supplying and mixing objects such as powder and particles, the thickness or density of the object may change within a time shorter than a time for acquiring the time domain waveform of terahertz pulse. However, the technology described in JP 2006-526774 A is not seen to consider such a change in thickness and density. Accordingly, there is a possibility that a component of the change is superimposed on the time domain waveform of measured terahertz pulse. Therefore, it is not easy to improve the analytic precision of information, such as component or particle size, of the object.